Fixed- and especially mobile-networks, such as Global System for Mobile communications (GSM), General Packet Radio System (GPRS) or Universal Mobile Telecommunication System (UMTS) are constantly evolving. GSM/GPRS and UMTS networks today offer both Circuit Switched (CS) connectivity and Packet Switched (PS) connectivity. The PS end-to-end connectivity with its capabilities for transmission of a wide range of data types may be used for offering multimedia services such as image, music and video transfer. The CS connectivity provides a link between two user equipment, or one or more terminals comprised by the user equipment, by means of one or more trusted network-nodes with a reliable and defined Quality of Service (QoS) for e.g. voice traffic.
Combinational networks, where at least two or more links of at least two different network types e.g. CS or PS, to one or more user equipment or terminals are established, are capable to deploy simultaneously both CS and PS connectivity to a user equipment or terminal, thereby facilitating services which perform their activity through PS-communication sessions, denoted as PS-sessions and CS communication sessions, denoted as CS-calls.
Services within a combinational network comprising networks of different network types such as a CS-network and a PS-network are denoted as combinational services. These combinational services which combine the traditional Circuit switched (CS) services with the emerging packet switched (PS) domain services, are being envisaged as the first pragmatic step to a network where all services will be provided by a PS domain architecture.
A network operator offering these combinational services would need a mechanism of charging the usage of these services, however methods to charge these combinational services are not yet in place. Hence a mechanism needs to be introduced to charge the end-users for usage of such combinational services.
Methods for charging a CS-call (post-paid as well as prepaid) are known. Methods also exist for packet based charging e.g. the Ericsson Flexible Bearer charging, or more generally known as Flow based charging.
What makes charging for a combinational service different from charging the components of a combinational service individually, is the additional flexibility and the desire indicated by operators to be able to charge for an aggregate service composed of a CS borne service and one or more PS borne services as opposed to native and established charging capabilities for CS and PS domains.
For example, if an A-party has an ongoing CS-call with a B-party, it should be possible for the A-party and the B-party to send pictures to each other and the resulting combinational call would be charged differently compared to the case whereby an Internet Protocol Multimedia Subsystem (IMS) session for the purpose of the picture transfer, is set up in isolation.
Methods do not exist for charging combinational services where a charging rate depends on services being correlated. While it is an option to limit combinational charging to charging for CS-calls and PS-session flows separately, there is no mechanism to introduce flexibility that makes it possible for an operator to apply charging a combination of a simultaneous CS-call and a PS-session by the same subscriber differently from prior art charging solutions where the CS-call and the PS-session are charged independently. Charging a combinational service, requires a check that the CS-call and the PS-domain based IMS-service are related to the same subscriber, and the CS-call and the PS-session are correlated to each other in that the same A-party and B-party are involved in the CS-call and the PS-session.
If charging events belonging to a CS-call, such as A-party-number, B-party-number, start-of-call timestamp and end-of-call timestamp, and charging events belonging to a PS-session towards an IMS service, such as start-of-transfer, amount-of-data and Session Initiation Protocol Universal Resource Identifier (SIP-URI), are stored and processed offline, it is not always possible to verify that the events belonged to a combinational call wherein the CS-call and the PS-session are correlated. In any case, establishing the aforementioned correlation in real time is likely to be more reliable than establishing this correlation offline.
As to verify whether a CS-call and a PS-session are correlated and hence combinational, a real-time check should be executed but the state of the art does not provide any solution that is effective, simple to implement and reliable.
Furthermore from a subscriber's point of view point, it should be ensured that any costs generated for the PS-session are billed in a reliable and trusted way in relation to his/her CS-call.
The problem the invention seeks a solution to is formulated as how to provide a method of checking the correlation of a simultaneous CS-call and one or more PS-sessions being deployed by a subscriber within a combinational telecommunication network.
Furthermore, any solution to said problem must fulfil as a requirement that the correlation check between the CS-call and the PS-session(s) shall not place additional requirements on the subscriber, i.e. the subscriber shall be able to spontaneously place a CS-call or start up a PS-session not knowing whether he/she will initiate another, related CS- or PS-service later during that call or session.